The present invention is directed to an extendable conveyor, such as a truck loader and/or unloader. While it may be useful with other types of extendable conveyors, the present invention is particularly useful in such a conveyor wherein the mechanically extendable section is supported in a cantilevered fashion by a support structure.
Extendable conveyors and, in particular, cantilevered supported extendable conveyors are known in the art. An example is disclosed in commonly assigned U.S. Pat. No. 5,351,809, the disclosure of which is hereby incorporated herein by reference. Because the extendable section is supported in a cantilevered fashion, it can be readily extended into, for example, a truck trailer in order to load and/or unload the trailer without regard for the condition of the floor of the trailer. One form of such an extendable conveyor has utilized a conveyor belt which is reeved with the booms of the extendable section in order to either supply articles to load the trailer or to withdraw articles to unload the trailer. In addition, a series of chains are utilized to either extend or retract the extendable section. Such an extendable conveyor as known in the '809 patent is fabricated from sheet metal members which are welded together in order to form the sections making up the mechanically extendable section.
While truck warehouses are often constructed with elevated docks, so that the floor of the trailer is at the same elevation as the warehouse floor, not all warehouses are constructed in this manner. This is especially true of small warehouses and warehouses located in city centers. In these types of warehouses, the floor of the warehouse is often at the level of the driveway supporting the truck trailer. This makes loading/unloading of the truck trailer more difficult. The warehouse end of the extendable conveyor is elevated so that the extendable section extends into the trailer at a proper operator height, which is deemed to be approximately waist high of the operator. Because the warehouse end needs to be elevated, the worker at the warehouse end must operate from an elevated platform and the conveyors servicing the extendable conveyor must also be elevated. Alternatively, in the case of a trailer unloader, a chute may be required in order to discharge the articles from the warehouse end of the extendable conveyor to the warehouse floor level.